The present invention relates to a spray gluing unit.
The invention finds application to advantage in the art field of packaging machines, and packers in particular, to which explicit reference will be made in the following specification albeit implying no limitation in scope.
The need exists in such machines for an adhesive substance to be applied to predetermined portions of paper material, for example flat diecut blanks folded ultimately into containers or packets, or to labels that will be affixed to such containers or packets.
It is standard practice in machines of the type in question to employ spray gluing units disposed facing a pass line, along which sheets for gluing are caused to advance, each such unit comprising at least one spray gluer with a nozzle connected to a circuit supplying the adhesive substance.
Spray gluing units of the aforementioned type betray the drawback that the nozzles need servicing and cleaning at frequent intervals, due especially to the fact that traces of the adhesive substance tend to dry on the nozzle tips whenever a temporary and/or prolonged stoppage occurs during operation of the machine.
In particular, the nozzles employed are furnished generally with outlets having tips of conical or frustopyramidal geometry, and it is on the outer surfaces of these tips that the sprayed adhesive becomes lodged and clings, due to its viscosity, forming encrustations and residues that compromise the correct operation of the gluer especially when the residues in question have dried.
The accumulated residues need to be removed, and accordingly the prior art embraces gluing units in which the nozzle is capable of movement between an operating position, in which the adhesive substance is sprayed onto the aforementioned sheets, and a cleaning station where the nozzle is subjected to the action of means serving to remove any deposits of the adhesive substance that may have dried, or simply to prevent the deposits from drying.
Alternatively, in certain types of machine, the means by which the residues of adhesive are removed can themselves be made capable of movement and thus offered to the nozzle, which remains substantially motionless in the operating position, although the cleaning operation is essentially no different.
The operation of cleaning the nozzle is in any event a difficult one. Owing to the aforementioned geometry of the nozzle, which presents sharp corner edges, cleaning means of mechanical type will tend to be particularly complex, whereas cleaning means of hydraulic type, using jets, require particularly high operating pressures that can produce overspray and cause the cleaning liquid to splash undesirably on other parts of the machine.
The object of the present invention is to provide a gluing unit unaffected by the drawbacks mentioned above, while being functional, economical and of compact dimensions.
The stated object is realized in a spray gluing unit according to the present invention, applicable to a product packaging machine, comprising at least one spray gluer equipped with a nozzle having a respective outlet from which an adhesive substance is directed at a wrapping material enveloping the products, also means by which to clean the gluing nozzle, the gluing nozzle and the cleaning means being capable of movement one relative to another for the purpose of cleaning the outlet.
To advantage, the spray gluer presents a surface surrounding and joined to an end face of the nozzle outlet, and cleaning means comprise means capable of interacting with the end face of the outlet and with the surrounding surface at least during the relative movement of the cleaning means and the nozzle, in such a way as to remove any residues of the adhesive substance.